Spinach Lasagna

1. FOR THE SAUCE: Bring 4 quarts water to boil in large pot. Fill large bowl with ice water. Add spinach and 1 tablespoon salt to boiling water and cook, stirring often until spinach is just wilted, about 5 seconds. Remove spinach with slotted spoon, transfer to ice water, and soak until completely cool, about 1 minute; drain spinach and transfer to clean kitchen towel. Wrap towel tightly around spinach to form ball and wring until dry. Chop spinach and set aside.
2. Melt butter in medium saucepan over medium heat. Add shallots and garlic and cook, stirring often, until shallots are softened, about 4 minutes. Add flour and cook, stirring constantly, until thoroughly combined, about 1-1⁄2 minutes; mixture should not brown. Gradually whisk in milk; increase heat to medium high and bring to boil, whisking often. Stir in bay leaves, nutmeg, 1⁄2 teaspoon salt, and pepper, reduce heat to low, and simmer, whisking occasionally, for 10 minutes. Discard bay leaves, then whisk in Parmesan until completely melted. Measure out and reserve 1⁄2 cup sauce in small bowl; press plastic wrap directly against surface, and set aside. Transfer remaining sauce to separate bowl and stir in chopped spinach, mixing well to break up any clumps; press plastic directly against surface, and set aside.
3. FOR THE CHEESE FILLING: Process cottage cheese, egg, and salt in food processor until very smooth, about 30 seconds.
4. Adjust oven rack to middle position and heat oven to 425 degrees. Pour 2 inches boiling water into 13 by 9-inch broiler-safe baking dish. Slip noodles into water, 1 at a time, and soak until pliable, about 5 minutes, separating noodles with tip of sharp knife to prevent sticking. Remove noodles from water and place in single layer on clean kitchen towels; discard water. Dry and grease dish.
5. Spread reserved 1⁄2 cup sauce evenly over bottom of prepared dish. Arrange 3 noodles in single layer on top of sauce. Spread 1 cup spinach mixture evenly over noodles, sprinkle with Parmesan, and top with 3 more noodles. Spread 1 cup more spinach mixture evenly over top, sprinkle with 1 cup fontina, and top with 3 more noodles. Spread 1 cup spinach mixture evenly over top, followed by cottage cheese mixture. For final layer, arrange remaining 3 noodles on top and cover with remaining spinach mixture. Sprinkle with remaining 1 cup fontina.
6. Cover dish tightly with aluminum foil that has been sprayed with vegetable oil spray and bake until edges are just bubbling, about 20 minutes, rotating dish halfway through baking. Remove dish from oven and remove foil. Adjust oven rack 6 inches from broiler element and heat broiler. Broil lasagna until cheese is spotty brown, 4 to 6 minutes. Cool lasagna for 15 minutes before serving.

SPINACH LASAGNA WITH PROSCIUTTO
Melt 2 tablespoons butter in sauce in medium saucepan over medium heat. Add 2 ounces thinly sliced prosciutto, chopped, and cook until crisp, 5 to 7 minutes. Remove prosciutto with slotted spoon and transfer to paper towel–lined plate; set aside. Add remaining 3 tablespoons butter to fat left in saucepan and melt over medium heat before adding shallots and garlic in step 2. Sprinkle crisp prosciutto over cottage cheese mixture while assembling lasagna.

SPINACH LASAGNA WITH MUSHROOMS
Melt 2 tablespoons unsalted butter in medium saucepan over medium heat. Add 8 ounces trimmed and thinly sliced white mushrooms and cook until softened and lightly browned, 8 to 10 minutes; transfer to bowl. Sprinkle softened mushrooms over cottage cheese mixture while assembling lasagna.